Body composition and chemotherapy-related toxicities in early-stage breast cancer: implications for personalized treatment strategies

Abstract Background Chemotherapy-related toxicity may result in dose reduction, treatment interruption, or premature discontinuation in patients with early-stage breast cancer. Conventional body surface area-based dosing does not adequately account for interindividual differences in muscle mass, adiposity, or fat distribution, which may influence drug disposition and treatment tolerance. Aims This study aimed to summarize the assessment methods, clinical indicators, potential mechanisms, and current evidence linking body composition with chemotherapy toxicity in early-stage breast cancer. Methods Relevant published literatures were comprehensively reviewed synthesize evidence on commonly used body composition assessment methods, including CT/MRI, DXA, BIA, and anthropometric measurements. Muscle-related, fat-related, and composite indicators were summarized, and their relationships with chemotherapy toxicity were analyzed. Results Body composition indicators derived from different assessment methods vary substantially in definition, calculation, and cutoff values. Reduced lean body mass, low skeletal muscle index, sarcopenia, myosteatosis, increased fat mass, visceral adiposity, and sarcopenic obesity have been associated with increased chemotherapy toxicity in breast cancer patients. Body composition may affect toxicity through altered inflammation, endocrine signaling, drug distribution, metabolism, renal function estimation, and systemic clearance. However, current evidence remains heterogeneous, with inconsistencies in diagnostic thresholds, assessment methods, chemotherapy regimens, and population-specific cutoffs. Conclusion Body composition is a promising biomarker for chemotherapy toxicity and guides personalized therapy, but prospective breast cancer-specific studies are required before body composition-guided dosing can be routinely implemented.